An N-substituted acrylamide or methacrylamide is a useful starting material for flocculants, textile, ion exchange resins, coatings, water-soluble films, photographic emulsions, etc.. It is conventionally produced by reacting an acrylic or methacrylic acid ester with amine. More specifically, an acrylic or methacrylic acid ester can be reacted with at least 2 mols of tertiary amino alkylamine at a temperature between 20.degree. C. and 200.degree. C., whereupon aminolysis of the ester group and Michael addition to the carbon-carbon double bond take place simultaneously to produce the corresponding beta-aminopropionamide as an intermediate, which is then decomposed at a temperature between 180.degree. C. and 300.degree. C. to eliminate the amine attached to the carbon-carbon double bond so as to give N-(tertiary aminoalkyl)acrylamide (see U.S. Pat. No. 3,878,247); or an acrylic or methacrylic acid ester can be reacted with an amine in gaseous phase in the presence of a solid acid catalyst such as vanadium-aluminum oxide at a temperature between 300.degree. C. and 550.degree. C. for a contact period of several seconds, to thereby produce the corresponding substituted acrylamide or methacrylamide (see U.S. Pat. No. 2,719,175). However, the first method involves several reaction steps and requires high operating temperatures, which leads to high energy costs, whereas the second method, which also uses high reaction temperatures, is accompanied by side reactions such as decomposition and polymerization, and the maximum yield of the product is only about 50%.
A method has recently been proposed to produce N-substituted acrylamide or methacrylamide by reacting an alkyl ester of acrylic or methacrylic acid with amine at from 50.degree. C. to 180.degree. C. in the presence of a catalytic amount of dialkyltin oxide (see U.S. Pat. No. 4,206,143). In this method, aminolysis of the ester group predominates over Michael addition to the carbon-carbon double bond, thereby producing the desired end product in a yield higher than was previously achieved. However, as described therein, even this method cannot produce the end compound without formation of a Michael addition product. As will be demonstrated in the Comparative Example herein, it has been confirmed by experiment that the method of U.S. Pat. No. 4,206,143 produces about 7 mol% of Michael addition products, one made up of the ester and amine, and the other made of the substituted amide and amine. When the reaction product is attempted to be refined by distillation, such Michael addition products are decomposed thermally and the amine is dissociated, thus failing to obtain an end product of high purity. It is therefore very desirable that the formation of Michael addition products in the reaction between alkyl ester of acrylic or methacrylic acid and amine be minimized.